For administration method of 4-biphenylacetic acid which is non-steroidal anti-inflammatory and analgesic agent, the gel preparation was developed to avoid the systemic side effects thereof and has been used clinically from early stage. However there are some disadvantages that the gel preparation soils the clothes at the time of administration, the gel preparation has to be administered frequently and furthermore the dosage of gel preparation is not regularized. Therefore, the cataplasm contains 4-biphenylacetic acid has developed (Japanese Patent Application Laid-Open No. 193728/1991), and has been marketed.
This developed cataplasm is the preparation that is nearly satisfactory in adhesive power and with the sustained effect of the active ingredient; however, further improvement is desired about continuous adhesive power and sustained effect of the active ingredient. Nevertheless, as for cataplasm, there is a problem in the limitation of the adhesive power and so on, and therefore, to solve these problems, plaster used oily tape as the base material is proposed (Japanese Patent Application Laid-Open No. 321624/1992).
In the plaster proposed in the above, crotamiton is used as a solvent for 4-biphenylacetic acid; however, the solubility of 4-biphenylacetic acid in crotamiton is about 7%, and using small amount of the solvent is insufficient for dissolving of 4-biphenylacetic acid. Furthermore, the crystallization of 4-biphenylacetic acid in the kneaded base material is recognized, and as the result, absorbability and sustained effect of the active ingredient are decreased. On the other hand, in the case of large amount of crotamiton is used for the solvent, there are some problems such as remaining of the base material on the skin by decrease of the adhesive power of the base material, and occurrence of skin irritation.
The inventors of the present invention had made intensive studies to overcome the above-mentioned problems, and succeeded to discover the present invention. That is, the present inventors found out that the plasters containing 4-biphenylacetic acid as an active ingredient in the adhesive base material essentially composed of styrene-isoprene-styrene block copolymer, N-methyl-2-pyrrolidone and polyethylene glycol possess excellent properties to solve such problems at a stroke.
Therefore, the purpose of the present invention is to provide the plasters containing 4-biphenylacetic acid as active ingredient having low degree of skin irritation and high safety margin, in which releasing of 4-biphenylacetic acid from the adhesive base material and sustaining pharmaceutical effect of the active ingredient are improved in comparison with conventional plasters.